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Topic: 5V relay for switching 120VAC (Read 3402 times)

I am building my own Mach 3 CNC pendant and I incorporated an on and off switch for convenience, without it, I will have to get down on my knees and reach behind the PC tower to toggle on and off. I want a simple one wire solution from the pendant to the tower, so I was going to use a DB9 cable. I need four pins for USB, two pins for E stop switch and this leaves three pins for power. I am not daft enough to think I could run 120v thru a DB9 cable, but even with proper gauge wire, I don't want high voltage running beside my communication wire, so I was going to send 5V from my computers PSU to the pendant and have it trigger a 120v relay.

No, you definitely do not want to run high voltage (120) with low voltage wiring. I mean it can be done, but it is not safe and can shock you or damage your equipment, so I say don't do it.Looks like that relay will work.And an led should be fine but you may need to run three wires, one +5VDC (can probably get it off the usb port).A ground for the LED (also off usb, possibly. usb is good for about 500 ma, so figure what kind of load will be on it.)And the wire back to relay to turn it on.Wire +5 to your switch.Other side of switch goes to the relay, also to the led.Other led wire goes to ground. (Also suitable resistor in line with led.)I can give you a simple diagram if you need it.